Vehicles often include a hydraulic braking system for reducing the speed of the vehicle and/or maintaining the vehicle in a stopped position. Typically, a hydraulic braking system includes a pneumatic/vacuum brake booster having an output rod, which is received by a master cylinder. Hydraulic brake lines fluidly couple the master cylinder to one or more hydraulic brake wheel cylinders. The brake booster receives a pedal rod, which is coupled to a brake pedal positioned within a cabin of the vehicle. In operation, the brake booster reduces the force required to activate the braking system by amplifying a force exerted on the brake pedal by an operator of the vehicle. The brake booster transmits the amplified force through the output rod to one or more pistons within the master cylinder. Movement of the pistons within the master cylinder provides fluid under pressure to each brake wheel cylinder through the hydraulic brake lines. Each of the brake wheel cylinders that receives the fluid under pressure, moves a friction material against a rotor or drum associated with a wheel and tire assembly of the vehicle. Moving the friction material against the rotor or drum decelerates the vehicle and/or maintains the vehicle in a stopped position. In response to the vehicle operator releasing the force upon the brake pedal, such that the brake pedal moves in a release direction to a deactivated position, the output rod of the brake booster and the master cylinder pistons move in the release direction, which deactivates the hydraulic brake wheel cylinders and permits the drum, rotor, wheel and tire assembly, and/or other elements to rotate freely.
In general, the brake booster includes a housing, the output rod, a diaphragm, and a valve. The diaphragm, which is coupled to the output rod, divides an internal cavity of the housing into a booster chamber and a vacuum chamber. The brake booster couples vacuum generated by a gasoline engine or a vacuum pump to the vacuum chamber, in order to maintain the vacuum chamber at a pressure less than the atmospheric pressure. The valve controls fluid flow between a working chamber portion and an atmosphere chamber portion of the booster chamber. Biasing members maintain the valve in a closed position, which separates the working chamber from the atmosphere chamber. When the valve is closed, the brake booster supplies vacuum to the working chamber, in order to maintain the working chamber and the vacuum chamber at the same pressure level. The approximately equal pressure on each side of the diaphragm causes the diaphragm to remain stationary. The valve opens in response to the vehicle operator exerting a force on the brake pedal and, in response, the negative pressure within the working chamber draws air from the atmosphere through the atmosphere chamber and the valve and into the working chamber. Therefore, when the valve is open the pressure in the working chamber becomes greater than the pressure in the vacuum chamber. The imbalance of pressure between the vacuum chamber and the working chamber tends to move the diaphragm and the output rod in the direction, which activates the hydraulic brake wheel cylinders. Accordingly, the imbalance of pressure amplifies the force exerted on the brake pedal and makes the braking system easier for users to operate.
Master cylinder and brake booster arrangements include numerous parts, making the arrangements relatively expensive and complicated to manufacture and assemble. Accordingly, there is a continuing need in the art to provide a master cylinder and brake booster arrangement, which is less complicated to manufacture and assemble and is therefore less expensive, more compact, and more reliable.